The present invention relates to a method of separating uranyl nitrate and plutonium nitrate from a mixed nitric acid solution containing uranyl nitrate and plutonium nitrate.
In particular, the separating method of the present invention can replace a partition process (a process in which uranium and plutonium contained in an extractant are separated from each other by the use of a difference in the distribution ratio therebetween) which has hitherto been carried out in the reprocessing of spent nuclear fuel.
In the reprocessing of spent nuclear fuel, uranium (U) and plutonium (Pu) are separated from each other by means of the partition process. That is, a nitric acid solution containing U, Pu and FP (fission products) is contacted with an organic solvent, such as tributyl phosphate (TBP)/n-dodecane, to thereby extract U and Pu in an organic phase (co-decontamination process). Subsequently, the organic solvent containing U and Pu is brought into contact with a nitric acid solution containing a reducing agent (such as uranous nitrate) to reduce Pu.sup.4+ into Pu.sup.3+ to be stripped or back extracted into a water phase while leaving U0.sub.2 2+ to remain in the organic phase (partition process). The U left remaining in the organic phase is later stripped with dilute nitric acid.
As described above, the partition process in which U and Pu are separated from each other utilizes the difference therebetween in the distribution ratio with respect to an extractant. However, the employed operations, such as extraction and stripping, are complicated, the amount of an extractant to be used is large, and the addition of a reducing agent is required.